Effect of Dielectric Thickness on Resistive Switching Polarity in TiN/Ti/HfO2/Pt Stacks (original) (raw)
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Resistive switching behavior in TiN/HfO2/Ti/TiN devices
2012 International Semiconductor Conference Dresden-Grenoble (ISCDG), 2012
This work reports the bipolar resistive switching behavior of more than 100 back-end-of-line (BEOL) integrated 600x600nm 2 TiNIHf02ffiffiN MIM devices in a 4 kbit memory array. Reliable current-voltage switching characteristics were only observed for devices with a thickness ratio of 1 (10 nm Hf02110nm Ti), indicating the importance of the interface chem istry of the TilHf02 interface. Moreover, the devices show good inter-cell uniformity and thus demonstrate promising prospects for embedded non-volatile memory (eNVM) applications.
Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena, 2011
The authors demonstrate bipolar resistive switching in TiN/ HfO 2 / Ti͑top͒ / TiN devices using a ͑Bi͒ complementary metal-oxide semiconductor ͑CMOS͒ compatible technology process. The device performance includes a cycling endurance in dc sweeping mode Ͼ10 3. The results suggest that HfO 2-based metal-insulator-metal devices with Si CMOS compatible metal electrodes may be well suited for future embedded nonvolatile memory applications. However, hysteretic current-voltage characteristics were only observed for a Ti top adlayer, whereas a Ti bottom adlayer integration did not show any resistive switching effect. Using x-ray photoelectron spectroscopy, the authors examined the interface chemistry of the Ti/ HfO 2 interface. It is clearly observed that Ti top adlayer deposition results in an increased nitrogen-and oxygen-gettering activity in contrast to Ti bottom adlayer. It follows that the formation of a nonstoichiometric HfO 2 layer at the Ti/ HfO 2 interface is crucial for resistive switching.
Nano-analytical investigation of the forming process in an HfO2-based resistive switching memory
Journal of Applied Physics
Metal oxide-based resistive random access memory devices are highly attractive candidates for next-generation nonvolatile memories, but the resistive switching phenomena remain poorly understood. This article focuses on the microscopic understanding of the initial forming step, which is decisive for the switching process. The integrated resistive switching memory effect in Ti/HfO 2 /TiWN metal insulator metal structures is studied. After forming, transmission electron microscopy investigations pointed out the presence of a funnel-shaped region, in the ON state of the cell, where slightly oxidized Ti (TiO x) was present within HfO 2 dielectric. Modeling of the measured ON state conductance of the cell with the semi-classical approximation is consistent with a conductive nanometric TiO x filament (or a sum of sub-nanometric TiO x filaments) present in the funnel-shaped region. The conductive area is likely formed by diffusion after the dielectric breakdown.
Resistive switching characteristics of Pt/CeOx/TiN memory device
Bipolar resistive switching memory (RRAM) relies on ion migration effects taking place at a conductive filament (CF). Understanding the evolution of the CF during set and reset transitions is essential for predicting RRAM scalability and for developing new methods for storage and computation. This work describes the evolution of the CF during bipolar resistive switching through numerical simulations of ion drift/diffusion. The defect distribution profile for increasing current after set transition and for increasing voltage during set transition are shown. Finally, the asymmetric shape of the CF is evidenced through polarity-dependent experiments and explained through numerical simulations.
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2011
The authors demonstrate bipolar resistive switching in TiN/ HfO 2 / Ti͑top͒ / TiN devices using a ͑Bi͒ complementary metal-oxide semiconductor ͑CMOS͒ compatible technology process. The device performance includes a cycling endurance in dc sweeping mode Ͼ10 3 . The results suggest that HfO 2 -based metal-insulator-metal devices with Si CMOS compatible metal electrodes may be well suited for future embedded nonvolatile memory applications. However, hysteretic current-voltage characteristics were only observed for a Ti top adlayer, whereas a Ti bottom adlayer integration did not show any resistive switching effect. Using x-ray photoelectron spectroscopy, the authors examined the interface chemistry of the Ti/ HfO 2 interface. It is clearly observed that Ti top adlayer deposition results in an increased nitrogen-and oxygen-gettering activity in contrast to Ti bottom adlayer. It follows that the formation of a nonstoichiometric HfO 2 layer at the Ti/ HfO 2 interface is crucial for resistive switching.
Nonvolatile resistive switching memories-characteristics, mechanisms and challenges
Progress in Natural Science: Materials International, 2010
This review presents a summary of current understanding of the resistive switching materials and devices which have inspired extraordinary interest all over the world. Although various switching behaviors and different conductive mechanisms are involved in the field, the resistive switching effects can be roughly classified into filament type and interface type according to their conducting behavior in low resistance state. For those filament based systems, the migration of metallic cations and oxygen vacancies, characterization of the filament as well as the role of Joule heating effects are discussed in detail. As to the interface based system, we describe the methods of modulating interface barrier height such as using different electrodes, inserting a tunnel layer. It is demonstrated that the switching mechanism can transform from one to another along the change of some specific conditions. We also give an overview on the latest developments in multilevel storage and the resistive switching in organic materials. In this paper, the solutions to address the sneak current problems in crossbar structure are discussed.
Bipolar resistive switching on Ti/TiO2/NiCr memory cells
Superficies y Vacío, 2017
We investigated the electric-field-induced resistance-switching behavior of metal-insulator-metal (MIM) cells based on TiO2 thin films fabricated by the reactive RF-sputtering technique. MIM cells were constructed by sandwiched TiO2 thin films between a pair of electrodes; Ti thin films were employed to form an ohmic bottom contact and NiCr thin films were employed to form Schottky top electrodes obtaining Ti/TiO2/NiCr MIM cells. Schottky barrier height for the TiO2/NiCr junction was determined according to the thermionic emission model by using the Cheung´s functions. SEM and Raman analysis of the TiO2 thin films were carried out to ensure the quality of the films. Current-Voltage (I-V) sweeps obtained at room temperature by the application of dc bias showed a bipolar resistive switching behavior on the cells. Both low resistance state (ON state) and high resistance state (OFF state), of Ti/TiO2/NiCr cells are stable and reproducible during a successive resistive switching. The res...
Enhanced bipolar resistive switching of HfO 2 with a Ti interlayer
Applied Physics A-materials Science & Processing, 2011
The characteristics of resistive switching of TiN/HfO2/Ti/HfO2/Pt/Ti stacks on SiO2/Si substrates were investigated and compared to TiN/HfO2/Pt/Ti stacks in order to study Ti interlayer effects on resistive switching. The Ti interlayers were deposited in situ during the reactive sputtering of HfO2 films. The current–voltage measurements showed that the Ti interlayers enhanced the memory window but reduced the endurance of SET/RESET operations. The energy filtered images by TEM showed asymmetric oxygen accumulation at the Ti/HfOx interfaces. Subsequent heat treatment improved the endurance of SET/RESET operation of TiN/HfO2/Ti/HfO2/Pt/Ti stacks.
Bipolar resistive switching in Cu/AlN/Pt nonvolatile memory device
Applied Physics Letters, 2010
Highly stable and reproducible bipolar resistive switching effects are reported on Cu/AlN/Pt devices. Memory characteristics including large memory window of 10 3 , long retention time of Ͼ10 6 s and good endurance of Ͼ10 3 were demonstrated. It is concluded that the reset current decreases as compliance current decreases, which provides an approach to suppress power consumption. The dominant conduction mechanisms of low resistance state and high resistance state were verified by Ohmic behavior and trap-controlled space charge limited current, respectively. The memory effect is explained by the model concerning redox reaction mediated formation and rupture of the conducting filament in AlN films.
Resistive switching characteristics of ytterbium oxide thin film for nonvolatile memory application
Thin Solid Films, 2011
This paper studies the effects of both the positive and negative forming processes on the resistive switching characteristics of a Pt/Yb 2 O 3 /TiN RRAM device. The polarity of the forming process can determine the transition mechanism, either bipolar or unipolar. Bipolar behavior exists after the positive forming process, while unipolar behavior exists after the negative forming process. Furthermore, the bipolar switching characteristics of the Pt/Yb 2 O 3 /TiN device can be affected by using a reverse polarity forming treatment, which not only reduces the set and reset voltage, but also improves the on/off ratio.